I have the following piece of code;
module Billing.Options
(
GlobalOpts(..)
, globalOptsParser
, parseDb
, parseSql
) where
import Options.Applicative
import Options.Applicative.Simple
import Options.Applicative.Types
import System.FilePath.Posix
import Text.Regex.PCRE
-- ------------------------------------------------------------
data GlobalOpts = GlobalOpts
{
optDb :: String,
optSql :: String
} deriving Show
-- ------------------------------------------------------------
globalOptsParser :: Parser GlobalOpts
globalOptsParser = GlobalOpts
<$> option (parseDb =<< readerAsk)
( long "db"
<> short 'd'
<> metavar "<DB name>"
<> help "dmt | report"
)
<*> option parseSql
( long "sql"
<> metavar "<SQL SELECT statement>"
<> help "sql select statement to use in order to generate JSON config file"
)
-- ------------------------------------------------------------
matches :: String -> String -> Bool
matches = (=~)
-- ------------------------------------------------------------
parseDb :: String -> ReadM String
parseDb val = do
if not (elem val ["dmt", "report"])
then readerError $ "Unknown DB, '" ++ val ++ "'"
else return val
-- ------------------------------------------------------------
parseSql :: ReadM String
parseSql = do
val <- readerAsk
if not (val `matches` "(?i)select .+ from .+")
then readerError $ "Please provide a valid SQL SELECT statement"
else return val
-- [EOF]
I'm testing my argument parser with the following code;
error' = let mp = runParser AllowOpts globalOptsParser ["-d", "billing"]
opts = ParserPrefs "suffix" False False False 80
in fst $ runP mp opts
The required arguments are,
-d <DB name>
--sql <SQL SELECT statement>
I want to test that I get the error message,
Missing: --sql <SQL SELECT statement>
when I only specify "-d billing".
The above test code gives the following output if I print the result,
Left (MissingError (MultNode [MultNode [MultNode [AltNode [Leaf (Chunk {unChunk = Just --sql <SQL SELECT statement>})]]]]))
Is there a way to generate the expected error message (String) from the above result (Either data type)? Does Haskell provide an obvious function to use for this purpose as I cannot find something in the documentation and googling for examples also didn't produce any answers.
If you look at the source code repository for optparse-applicative (link) you'll see that it itself has a test suite in the tests subdirectory.
A routine which looks like it does a lot like what you want is checkHelpTextWith in the file tests/Test.hs:
checkHelpTextWith :: Show a => ExitCode -> ParserPrefs -> String
-> ParserInfo a -> [String] -> Assertion
checkHelpTextWith ecode pprefs name p args = do
let result = execParserPure pprefs p args
assertError result $ \failure -> do
expected <- readFile $ name ++ ".err.txt"
let (msg, code) = renderFailure failure name
expected @=? msg ++ "\n"
ecode @=? code
This function expects an option parser to fail and compares the error message with the contents of a file.
The main functions of interest are:
execParserPure :: ParserPrefs -> ParserInfo a -> [String] -> ParserResult a
renderFailure :: ParserFailure ParserHelp -> String -> (String, ExitCode)
The String returned by renderFailure is the error message.